Digging device null a little more than of shielded

摘要

PURPOSE: To make easily outbreak-excavation even if a bedrock is a hard soil layer or a sand gravel layer mixed with cobbl stone and to make it possible to ensure a sufficient amount of outbreak and durability. ;CONSTITUTION: A roller bit 13 having a plurality of disk-like blades 13a are provided to a bearing body 15 located around the outermost peripheral surface section of a revolving cutter heard 5 and sliding in the direction of the radius with the expansion of a hydraulic jack 18 in a rotatable manner in a state to incline the axial center against a driving direction. The ends of the blades of the roller bit 13 are projected and recessed from a normal excavation face 24 of the cutter head 5 with the hydraulic jack 18.;COPYRIGHT: (C)1995,JPO